Telephone signaling system



Oct. 23, 1928,'

C. S. DEMAREST ETAL TELEPHONE SIGNALING S'Yszru Filed nay 19, 1926 SiN l w @@mwmw.. m#

INvE/voles mar/rest a@ 0, .Zay/@a5 TTORNE Y Patented Oct. 23, 1928.

STATES PATENT oFFicE.

CHABLESISSDENABEST, 0E mneiiwoon,l NEW JERSEY, AND OWEN H. LoYNEs,v 0E In'noox'mrmNaw Yonx, ASsIGNons To AMERICAN TELEPHONE AND TELEGRAPH coliPANn: CORPORATION or NEw'Yonx.

.TELEPHONE SIGNALING SYSTEM.

` Application led lay 19,

` l'lhis"inventionfrelates toy telephone signalingjsystemsfand more particularly to arrangements foi if'a'nsmitting supervisory signais'y between tral office stations.

v y {In} thefoperation of a group of telephone circuits' improved traiic methods, a number, of fsi'ipervisory signals are required. Facili es' fo the transmission of these su isory als are sometimes not available. as 'the c ot' radio speech channels; aiifcl'finthef case'pf l.wire circuits, they canno i always "hefobltained unless there are sacrificed 'fa'cilitieslforthe transmission of Morse,telegraphisignals over the telephone circiiitsf;y therinore, with the piesent standardff lities "for" signaling over voice l precautions must be taken 1n nst interference with the ice currents, and in order nterference" from other voice interference caused in other s df Yapplicantsinventon to erl ysory signals in cases in which the a ies cannot be obtained bly wirefmeana'as" Ii' the `case of radio s pee'c cha nelsfand, the case of wire circuits, to nals without any sacrifice D v t" leg h facilities and without any1 y ypes nterference mentioned above. "Applicants'f n cco'mplish .this object by transmitting the supervisory signals for rallying d y mittiii'g hyapplicantslmeans the signals emi loyedfi t hefso-,called two-Way straighttliodof operation, in which the s "a y k"ftwowaythat is` so that apa-Ilma e' voriginated atv either stationand in W ich lthe operators talk on the circuits''ial's'oiuseid"for the subscribers conversation;insteadfuising'a separate call circuit. "Witliref enceto the accompanying drawtati is a telephone central oiiice n netted with a distant central oliilcefstaftioiigBby a plurality of voice channelsfi'vhich be ordinary Wire circuits, carrier' circuits', or radio channels. The systeiir'fis' ifequipped for operation in 1926. Serial No. 110,252.

either direction, that is, for the initiation of following apparatus at each station, in association with each voice channch'is usually found at central otiice stations equipped for this method of operation; a cord for outgoinglr calls, a cord for incouiing calls, a jack for outgoing calls, a switching trunk associated with the inward cord, a first annunciator associated with the inward cord, and a second annunciator associated with the outward cord. Applicants provide at each station means for transmittin radio signals and means for receiving ra io signals. In addition, there are provided at cach station, in association with each of the voice channels, means for producing radio signaling current for transmission, and means for suitably tuning the radio receiver. For each voice channel served, there is required one radio signaling frequency for signaling in each direction, the signaling current producer associated with that channel at each station producing an a1- ternating current of a predetermined frequency and the receiver at the other station being correspondingly tuned by the circuit associated with that channel. It is to be understood that only the apparatus associated with one voice channel is shown in full, the apparatus peculiarly associated with the other channels being merely indicated and its connection to the radio transmitting and receiving apparatus shown.

The details of the signaling system will be clearly understood from the following description of the operation thereof.

If a subscriber directly connected with the central office station A wishes to communicate with a subscriber connected to station B, the operator at station A inserts the toll cord terminating in plug P1 into jack J at an outgoing position. Battery from the sleeve of the toll cord causes the operation of relay C. The operation of relay C in turn causes relays D and E to operate. The operation of relay E transfers the connection of the toll line from the plug P which is used for incoming calls to the out-- ward jack J'. The operation of rela D connects the oscillator O, which pro uces a high frequency signaling current, through 1 lamp L -c uding the lamp the tuned circuit F associated with the voice channel under consideration and the common amplifier G to the transmitting antenna of station A. The radio signal is transmitted to station B, received in the receiving apparatus of that station, and changed in fr uency (an oscillator belng associated with t e fre uency changer). The signal is then passed through the common amplifier H the tuned circuit 'K associated with the voice channel under consideration, and the rectifier M to the rclay N, which operates. The operation of relay N places ground over the leadS to the standard call circuit toll line, of which the essential parts are here shown symbolically. The ground on lead S causes relay Q to operate, which operation closes the circuit including the associated with the toll line at the incoming position, causing the lamp to light. The operator at station B is thus informed that a callis waiting on the particular line under consideration.

As is well understood in the art, the call circuit toll line is so arranged that the operators telephone set is connected automatically to the 4incoming end of the toll line on which a signal is waiting. When the called subscribers number .has been transmitted over the toll circuit to the operator at station B, the lug P of the incomin circuit at station is connected to the to switching trunk, and Ithe latter in `vturn is connected to the subscribers line. The connection of the plug P and the switching trunk causes the operation of relay U. The o ration of this rela brakes the circuit inextinguishing that lam and also opens the contact z.

Vien the subscribers line has been connected to the circuit at station B, battery over leads T and R causes the operation of relay- V', which in turn causes relay D to operate. The operation of relay D connects the oscillator O, which produces a hi h f uen signalin current throu h th tunlelqcircilyit F associated with the voigce channel under consideration and the common amplifier G to the transmitting antenna of station B. A radio signal is sent to station A, being received in the receivin antenna of that station. This signal is c anged in frequency and passed through the common amplifier H, the tuned circuit K yassociated with the voice channel under consideration, and the rectifier M to the relay N, whichI operates. Since relay C at station A is a ready operated, the operation of' relay N serves to connect the resistance X to ground in parallel with the windin of re ay C The value of thisresistance is so chosen with relation to the resistance of relay C that the connection to ground of the two resistances in parallel causes the operation of a marginal relay in the sleeve of the toll cord at thetoutgoin position. This mar- 'nal relay controls t e supervisory lamp in lle toll cord, which now lights. I

When the subscriber at station B has answered, relay V releases, causing the release of relay D and the removal of the radio signal sent to station A'as described above. Consequently, relay N at station A will release, and resistance-X will beremoved from the circuit including the marginal relay in the sleeve of the toll cord, the result being that the supervisory lamp in the toll cord is extinguished.` If the subscriber at station B operates his switch hook, relay V will follow this operation, that is, the relay will be o erated when the hook is down, and release when the hook is up. Relay D will follow the operation and will transmit radio -signalin current pulses to station A where relay is caused to operate and release, placinf'lgx resistance X in circuit intermittently. e result is'the flashing of the supervisory lamp in the toll cord at the outgoing position.

When the called subscriber at station B hangs up his receiver, the supervisory lamp at station A will be lighted steadily, as will be understood from the operations described above. The operator at station Athen removes theA plug P1 at the outgoing position from the jack J, releasing relays C, D and E. The release of relay D causes the radio signal, which was continuously transmitted from oscillator O during the period of connection of the cord and the jack J, to be removed. Accordingly, at station B relay N will release, this relay having been operated during the same period. The release of relay N causes the release of relay Q. Since relay U remains operated, the release of relay Q will close the circuit including the lamp L associated with the incoming position at station B, causing this lamp to light. This indicates to the operator at statlon B that the plug P assoclated with the lamp is to be vremoved from the toll switching trunk. Upon the removal of the plug, the lamp L is extinguished.

It is to be understood that only so much of the terminal apparatus at the twoh stations, which is old and well understood in the art, is shown in the drawing as ap ears to be necessary to an understanding o applicants invention.

The operation of applicants system in connection with a call initiated at station B is similar to the operation in the opposite direction, and will now be traced briefly. The operator at station B inserts plug l2 into the jack J, causingv the operation of relay C', which, in turn, causes relays D and E to operate. U on the operation of relay D', a radio signa is transmitted from the oscillator O to relay N at station A through tuned circuit F', amplifier G', translll tion B to station A, the operator at station A inserts plug P into Ithe toll switching trunk. Relay U is operated and extinguishes lamp L. Battery over leads T and R causesl relay V to operate, this operation station B then removes the resulting in the operation of relay D. Upon the operation of rela D a radio signal is transmitted from oscillator O at station A to relay N at stationv B through tuned circuit F amplifier G, transmitting antenna of.

station A, receivin antenna of station B, amplifier H', tune circuit K and rectifier Since relay C at station B remains operated, the operation of relay N connects the resistance X `to ground in parallel with the winding of relay C', and the marginal relay in the toll cord at the outgoing position\is operated, lighting the supervlsory lamp associated with the toll cord.

When the subscriber answers at station A, relays V and D release, removing, the radio signal which wastransmitted to station B. Relay N at station B` releases in response, and resistance X is removed from the sleeve circuit of the toll cord, the result being that the supervisory lamp is extinguished. If the subscriber at station A operates his switch hook, the result, as described above, is the lashingvofV the supervisory `lamp in the toll cord at the outgoing osition of station B. When the called su scriber at station A hangs up his receiver, the supervisory lamp at the outgoin position of station B remains steadily lig ted. The o erator at lug 2, thereby releasing relays C', D and The release of relay D results in the removal of the radio signal to station A, the release of relays` N and Q, at station A, and the lighting of lamp L associated with plug P at station A. This gives the indication to the operator at station A that plug P is to be removed. The removal of this plug extinguishes lamp L.

While applicants invention has been disclosed in one specific embodiment which is deemed desirable, it is to be understood that it is -capable of embodiment in many other and different forms without a de arture `from the scope of the invention as de ned in the appended claims.

What is claimed is: 1. In a telephone system including two central oice sta-tions and a voice channel connecting said stations, a cord at each station for outgoing calls, a cord at each station for incoming calls, a jack at each station for outgoing calls, a switching trunk associated with the inward cord at each station, a first annunciator associated with said inward cord at each station, a second annunciator associated with the outward cord at each station, means at each station for generating and transmitting radio signals, means at each station for receiving radio signals transmitted from the other station, automaticmeans at each station, responsive to the connection of the outward cord and the outward jack, for connecting the voice channel to the outward jack and simultaneously'therewith operating the radio signal generating and transmitting means at that station to send an initial radio signal to the other station, automat-ic means at each station for operating the first annunciator at that station in response to said initial radio signal received from the other station, automatic means at each station for terminating the operation of said first annunciator in response to the connection at that stat-ion of the inward cord and the switching trunk, automatic means at each station, responsive to the How of direct current over the switching trunk at that station, for operating the radio signal generating and transmitting means at that station to send a responsive radio signal to the other station, automatic means at each station for operating the second annunciator at that station upon the reception of said responsive radio signal from the other station, automatic means at each station, responsive to the lcessation and resumptlon of the flow of direct current over the switching trunk at that station, foi' terminating the o eration of and re-operating, res ectively, t e radio signal generatin an transmitting means at that station and the responsive second annunciator at the other stat-ion, automatic means at each station, responsive to the disconnection of the outward cord and the outward jack, for terminatin the transmission of the initial radio signa from that stat-ion, and automatic means at each station for re-operating the first annunciator at that station in response to the'termination of the initial radio signal received from the other station.

y2. In a telephone system including two central oice stations and a plurality 'of voice channels connecting said stations, means at each station for transmitting radio signals, means at -each station for receiving radio signals, and at each station in association with each voice channel the following: 'a cord for outgoing calls, a cord for incoming calls a jack for outgoin calls, a -switching trunli associated with t e inward cord, a first annunciator associated with said inward cord, a second annunciator associated with the outward cord, means for producing signaling current of a frequency peculiar to that station and to that voice channel, `means for tuning the lsignal receiving means at that station to the peculiar frequency produced at the other station and corresponding to that voice channel, automatic means, responsive to the connection of the outward cord and the outward jack, for connectinoV the voice channel to the outward jack and simultaneously therewith connecting the current producing means to the radio signal transmitting means at that station, causing.,1r said transmitting means to send an initial radio signal, of the peculiar frequency, to the other station, automaticmeans for operating the first annunciator atv that station in response to said initial radio signal, of the predetermined frequency, received from the other station, automatic means for terminating the operation of said first annunciator 1n response to the connection at that station of the inward cord and the switching trunk, automatic means, responsive to the flow of direct current over the switching trunk at that station, for connectin the current producing means to the ra io signal transmitting means at that station, causing said transmittinff means to send a responsive radio signal, of the peculiar frequency, to the other station, automatic means for operating the second annunciator at that station upon the reception of said responsive radio signal, of the predetermined frequency, from the other station, automatic means, responsive to to the'cessation and resumption of the flow of direct current over the switching trunk at that station, for disconnceting the current producing means from the radio signaloperating the first annunciator at that station 1n response to the termination of the initial radio signal, of the predetermined frequency, received from the other station. In testimony whereof, we have signed our names to this specification this 18th day of May, 1926.

CHARLES S. DEMAREST. OWEN H. LOYNES. 

